Coordination complexes as polyesterification catalysts

ABSTRACT

The process and the catalyst used therein for producing polyesters and copolyesters, useful for making films and fibers, by the polycondensation of dicarboxylic acids and aliphatic glycols using coordinations complexes of metal halides and silicon compounds as catalysts.

BACKGROUND OF THE INVENTION

The production of polyesters and copolyesters of dicarboxylic acids andaliphatic glycols has been carried out commercially for many decades.Among the earliest disclosures relating to the production of polyestersand copolyesters is the disclosure in U.S. Pat. No. 2,465,319, issuedMar. 22, 1949. Since this disclosure many variations have been made inthe process and many catalysts have been discovered and patented. OnDec. 8, 1970, there issued U.S. Pat. No. 3,546,179, which is directed tothe use of compounds containing both silicon and phosphorus atoms acompounds as a catalyst for the production of such polyesters andcopolyesters.

The use of metal halides and certain silicon compounds as catalysts inthe polycondesation of dicarboxylic acids and aliphatic glycols isdisclosed in U.S. Pat. Nos. 4,143,057; 4,254,241; and U.S. Pat. No. Re.30,554. The metal halides employed in the examples therein arenecessarily employed with solvent present. In addition these compoundstend to be hydrolytically unsatable and, thus, require careful hanldingduring their use. Thus, although these catalysts are highly advantageousit would be highly desirable to have a catalyst that may be of usewithout a solvent and which is hydrolytically stable.

SUMMARY OF THE INVENTION

It has now been found that coordination complexes of a metalalkoxyhalide and a silicon compound, as hereinafter defined, areexcellent polyesterification catalyst complexes for the production ofpolyesters and copolyesters useful for making films, fibers and othershaped articles.

DESCRIPTION OF THE INVENTION

In the production of polyesters and copolyesters the reaction isgenerally considered a dual or two stage reaction. In the first stageesterification or transesterification occurs and in the second stagepolycondensation occurs as follows: ##STR1## This invention is concernedwith novel polyesterification catalyst compositions and processes forproducing polyesters using such catalyst compositions.

The novel catalyst compositions of this invention are coordinationcomplexes of (A) a metal alkoxy halide and (B) a silicon compound, ashereinafter more fully defined. The use of these catalyst complexes orcompositions results in the elimination of the use of a solvent for thecatalyst, provides a less moisture sensitive, more hydrolytically stablecatalyst and results in the production of polyesters and copolyesters ofhigh degrees of polycondensation that are characterized by high meltingpoint, high elongation at break, good tensile strength and goodstability to heat and light.

The first stage esterification or transesterification reaction iscarried out in the traditional manner by heating the mixture at betweenabout 150° C. and about 270° C., preferably between about 175° C. andabout 250° C. During this stage any of the well-known esterification ortransesterification catalysts can be used, illustrative thereof one canmention zinc acetate, manganese acetate, cobalt (I) acetate, zincsuccinate, zinc borate, magnesium methoxide, sodium methoxide, cadmiumformate, and the like. The concentration thereof is that conventionallyused, namely between about 0.001 and about one percent by weight, basedon the weight of dicarboxylic acid compound charged. It is preferablybetween about 0.005 and about 0.5 percent by weight and more preferablybetween about 0.01 and about 0.2 percent by weight.

In the second stage, or the polycondensation, the coordination complexcatalysts of this invention are useful. These novel coordination complexcatalysts comprise two essential components. The first component is ametal alkoxy halide and the second component is one or more of thehereinafter defined silicon compounds.

The metal alkoxy halide used to produce the coordination complexesuseful as catalysts are the alkoxy halides of the metals titanium,zirconium, zinc, germanium, tin, lead, antimony and bismuth; preferablytitanium, germanium and antimony; and most preferably titanium. Themetal alkoxy halides useful as catalysts are of the general formula:

    M(OR).sub.a X.sub.b

wherein M is the metal and is at least one of titanium, zirconium, zinc,germanium, tin, lead, antimony and bismuth; R is alkyl, aryl, alkylaryl,arylalkyl or haloalkyl having between 1 and about 20 carbon atoms,preferably having between 1 and about 4 carbon atoms; a and b are eachan integer having a value of from 1 to 3; the sum (a+b) is equal to orless than 4; and X is at least one of F*, Cl, Br or I with the provisiothat when M is antimony a is an integer having a value of from 1 to 4and the sum (a+b) is equal to or less than 5. Illustrative of suitablemetal alkoxy halides one can include the mono-, di-, and tri-alkoxybromides, alkoxy chlorides, alkoxy fluorides and alkoxy iodides oftitanium and zirconium; the mono- and di-alkoxy bromides, alkoxychlorides, alkoxy fluorides and alkoxy iodides of zinc, germanium, tin,antimony, bismuth and lead including the mixed bromide-chlorides,bromide-iodides and chloride-iodides of tin. The preferred metal alkoxyhalides are the haloalkoxy titanates. These metal halides are well knownto the average chemist and are fully enumerated in chemical handbooks tothe extent that specific naming thereof is not necessary herein toenable one skilled in the art to know chemical names of the specificmetal alkoxy halides per se; see the The Organic Chemistry of Titanium,Feld and Cowe, Butterworth & Co., Ltd. (1965).

In producing the coordination complexes useful as catalysts, the molarratio of metal alkoxy halides to silicon compound in the coordinationcomplex can vary between about 2:1 and about 1:10; preferably betweenabout 1:1 and about 1:7, and most preferably between about 1:1 and about1:2.

In the polycondensation reaction the coordination catalyst complex ispreferably used in an amount of between about 0.01 and about 0.2 weightpercent, or higher, based on the weight of dicarboxylic acid compoundcharged, more preferably 0.01 to 0.06 weight percent. Although anycatalytically effective amount can be employed. As used in thisapplication the term "dicarboxylic acid compound" means both the freedicarboxylic acids and the esters thereof.

The dicarboxylic acid compounds used in the productionof polyesters andcopolyesters are well known to those skilled in the art andillustratively include terephthalic acid, isoterephthalic acid,p,p'-diphenyldicarboxylic acid, p,p'-dicarboxydiphenyl ethane,p,p'-dicarboxydiphenyl hexane, p,p'-dicarboxydiphenyl ether,p,p'-dicarboxyphenoxy ethane, and the like, and the dialkyl estersthereof that contain from 1 to about 5 carbon atoms in the alkyl groupsthereof.

Suitable aliphatic glycols for the production of polyesters andcopolyester are the acyclic and alicyclic aliphatic glycols havingbetween about 2 and 10 carbon atoms, especially those represented by thegeneral formula HO(CH₂)_(p) OH, where p is an integer having a value ofbetween about 2 and about 10, such as ethylene glycol, trimethyleneglycol, tetramethylene glycol, pentamethylene glycol, decamethyleneglycol, and the like.

Other known suitable aliphatic glycols include1,4-cyclohexanedimethanol, 3-ethyl-1,5-pentanediol,2,2,4,4-tetramethyl-1,3-cyclobutanediol, and the like. One can also havepresent a hydroxylcarboxyl compound such as 4-hydroxybenzoic acid,4-hydroxyethoxybenzoic acid, or any of the other hydroxylcarboxylcompounds known as useful to those skilled in the art.

It is also known that mixtures of the above dicarboxylic acid compoundsor aliphatic glycols can be used and that a minor amount of thedicarboxylic acid component, generally up to about 10 mole percent, canbe replaced by other acids or modifiers such as adipic acid, sebacicacid, or the esters thereof, or with a modifier that imparts improveddyeability to the polymers. In addition one can also include pigments,delusterants or optical brighteners by the known procedures and in theknown amounts.

The polycondensation reaction is generally carried out at a temperaturebetween about 225° C. and about 325° C., preferably between about 250°C. and about 290° C. at reduced pressure and under an inert atmosphere.These traditional reaction conditions for the polycondensation reactionare well known to those skilled in the art.

The silicon compounds that are used in conjunction with the metal alkoxyhalide to produce the coordination complex catalyst of this inventionare represented by the following generic formulas: ##STR2##

X is hydrogen or methyl and is methyl only when m is one;

R* is alkyl or haloalkyl having from 1 to 4 carbon atoms;

R** is methyl, ethyl, butyl, acetoxy, methoxy, ethoxy or butoxy;

R is methyl, ethyl, butyl, methoxy, ethoxy, butoxy, or trimethylsiloxy;

R' is methyl, methoxy, ethoxy, butoxy or trimethylsiloxy;

R" is methoxy, ethoxy, butoxy, trimethylsiloxy or vinyldimethylsiloxy;

R'" is methyl, ethyl, butyl, or trimethylsilyl;

Me is methyl;

Z is methyl or T;

Q is an NCCH₂ --, NH₂ CH₂ NHCH₂ --, NC-- HS-- or HSCH₂ CH₂ S-- group;

n is an integer having a value of from 2 to 5;

m is an integer having a value of zero or one;

x is an integer having a value of from 1 to 100; and

y is an integer having a value of from 1 to 100.

Subgeneric to the silicon compounds represented by formula (I) are thecompounds represented by the following subgeneric formulas: ##STR3##

Subgeneric to the silicon compounds represented by formula (II) are thecompounds represented by the following subgeneric formulas: ##STR4##

Illustrative of the silicon compounds which may be employed in formingthe polycondensation catalyst of the invention are the following:beta-cyanoethyl triethoxysilane, gamma-mercaptopropyl triethoxy-silane,gamma-aminopropyl triethoxysilane, diethoxy-phosphorylethyl methyldiethoxysilane, vinyl tri-ethoxysilane, vinyl trimethoxysilane, vinyltri-acetoxysilane, gamma-methacryloxypropyl trimethoxy-silane,diethoxyphosphorylethyl heptamethyl cyclo-tetrasiloxane, trimethyl silylterminated copolymer having dimethylsiloxy and methylvinylsiloxy unitsin the molecule, beta-cyanoethyl trimethylsilane, gamma-(2-aminopropyl)triethoxysilane, S-beta(2-mercaptoethyl) mercaptoethyl triethoxysilane,beta-mercaptoethyl, vinyl methyl diethoxysilane, vinyl methyldi(trimethylsiloxy)-silane, tetramethyl divinyl disiloxane, heptamethylvinyl cyclotetrasiloxane, 1,3,5,7-tetramethyl 1,3,5,7-tetravinylcyclotetra-siloxane, diethoxyphosphorylethyl methyl diethoxy-silane,diethoxyphosphorylisopropyl triethoxysilane, diethoxyphosphorylethylmethyl di(trimethylsiloxy)-silane, heptamethyl diethoxyphosphorylethylcyclo-tetrasiloxane, 1,3,5,7-tetramethyl1,3,5,7-tetra(di-ethoxyphosphorylethyl)cyclotetrasiloxane,1,1,3,3-tetramethyl-1,3-di(diethoxyphosphorylethyl)-disiloxane.

In a typical polycondensation reaction, the prescribed amounts ofdicarboxylic acid compounds, diols, and catalysts are charged to thereactor. The reaction mixture is then heated under an inert gasatmosphere at a temperature of between about 180° C. and about 210° C.to effect the initial esterification or transesterification. Thereafter,a substantial amount of the glycol is removed and thetransesterification is completed by heating the reaction mixture at atemperature of from about 225° C. to about 235° C. The second stagepolycondensation reaction is then carried out by heating the reactionmixture at a temperature of from about 225° C. to about 325° C. under areduced pressure of from about 0.1 mm. to about 20 mm. of mercury,preferably below about 1 mm. The use of the catalyst complexes ormixtures of this invention has often resulted in shorter overallreaction periods, decreased formation of glycol dimer, e.g. diethyleneglycol, and resulted in the absence of a solvent for the catalyst.

EXPERIMENTAL PROCEDURE

The following examples were carried out by preparing the haloalkoxytitanate by preparing a solution of the alkoxy titanate or haloalkoxytitanate and an acetyl halide (acetylchloride and acetyl bromide wereemployed) into a reaction flask (as a standard 3 neck-round bottomflask) equipped with a mechanical stirrer condenser and dropping funnel.The acetyl halide was slowly added to the titanate. The mixture wasrefluxed for about 2 to 21/2 hours in an oil bath at a temperature ofabout 70° C. and 80° C. The resulting mixture was distilled under vacuumwith fractions being analyzed as set forth in the following examples.

The titanium alkoxyhalides formed above was then reacted with a siliconcompound, as hereinbefore described and as set forth in the examples.The resulting mixture, i.e., the polycondensation catalyst, was analyzedby microanalysis.

The polycondensation catalyst was then employed as a polycondensationcatalyst by mixing with dimethyl terephthalate (736 grams) ethyleneglycol (542 grams) and manganese acetate (0.222 grams). Thetransesterification reaction was carried out by heating the mixture toabout 178° C. to about 190° C. for a period of time (about 3 hours)under an argon atmosphere with methanol being distilled from thereaction mixture. The temperature was then raised to about 230° C. andmaintained for about one hour to complete the transesterification step.The temperature was then raised to about 280° C. and the pressure wasreduced to below about 1 millimeter of mercury and the polycondensationprocess was carried out. During the polycondensation reaction themixture was stirred with a mechanical stirrer and a small amount of astabilizer was added when the mixture was at a temperature of about 250°C. and at 5 millimeters of mercury. The amount of stabilizer employed ineach example was 0.325 grams. The polycondensation reaction wasterminated when the intrinsic viscosity was 0.57, a typical value for acommercially acceptable polyester, and the time required to obtain theintrinsic viscosity was recorded as the polycondensation time (the timefrom reaching 1 mm mercury pressure to when the polyester has anintrinsic viscosity was 0.57). The intrinsic viscosity determinationswere made by preparing a solution of 0.5 weight percent of polyester ino-chlorophenol and measuring its viscosity at 25° C. in an Ubbelohdeviscometer.

The whiteness of the polyester was measured by use of a HunterlabTristimulus (x,y,z) Colorimeter D-25 which uses filters that approximatespectrally the standard observer functions of the eye and measure colorin terms of the parameters x,y,z which are obtained from the HunterlabTristimulus (x,y,z) Colorimeter. The b value is an indication of theyellowness or whiteness of the polyester and is determined by theequation: ##EQU1##

The lower the value of b the less yellow is the polyester. Themeasurement of b is made using a 2 inch square block of polyester resinafter the polyester resin has been polished. A positive b valueindicates that some yellow exists while a negative b value indicatessome blue exists.

STABILIZER

The stabilizer was prepared by charging 57 grams (0.0648) mole) of ethylacetate (solvent), 54.9 grams of superphosphoric acid (105%), 18.0 grams(0.170) mole) of diethylene glycol and 330 grams (5.4 mole) of propyleneoxide into a 3-neck round bottom flask equipped with a mechanicalstirrer and a condenser. The superphosphoric acid was added first withethyl acetate and diethylene glycol then being added. The reactionmixture was cooled to about 20° C. and the propylene oxide was addeddropwise under an argon atmosphere while the reaction mixture wasstirred and cooled by an ice bath. The temperature of the reactionmixture was kept at between about 30° and 40° C. during the addition ofthe propylene oxide which addition took about two hours.

The reaction mixture was refluxed for 2 hours at about 44° C. andsubsequently stripped in vacuum of excess propylene oxide to give 265grams of the stabilizer product having 6.26 weight percent phosphorusand characterized by an infrared spectrum having strong bands at 3400cm⁻¹, 1737 cm⁻¹, 1455 cm⁻¹, 1375 cm⁻¹ and 1260 cm⁻¹.

EXAMPLE 1

The coordination complex component monochloro tri(isopropoxy) titanatewas produced by preparing a mixture of 65.0 grams of tetra isopropyltitanate and 18.0 grams of acetyl chloride in a reaction flask (astandard 3 neck-round bottom flask) equipped with a mechanical stirrer,condenser and dropping funnel. The acetyl chloride was slowly added tothe tetra isopropyl titanate to prepare the solution. The mixture wasrefluxed for 21/2 hours in an oil bath at about 70° to 80° C. and thendistilled in vacuo. Microanalysis of the fraction distilling at about135° C. to 140° C. (18 mm Hg) showed 40.19 wt. percent carbon; 8.13 wt.percent hydrogen; and 14.19 wt. percent chlorine.

The above product (26.3 grams) was mixed with 34.0 g of di(isopropoxy)phosphoryl ethyl methyl diethoxysilane. An exothermic reaction occurredand a yellow oil solution was observed.

The resulting catalyst was used in the preparation of polyester, asabove described, which had a molecular weight of 17,800 and a b-value of7.4.

EXAMPLE 2

The coordination complex component monobromo tri(isopropoxy) titanatewas produced by preparing a solution of 34.8 grams (0.122 mole) of tetraisopropyl titanate and 14.8 grams (0.122 mole) of acetyl chloride in areaction flask (a standard 3 neck-round bottom flask) equipped with amechanical stirrer, condenser and dropping funnel. The acetyl chloridewas slowly added to the tetra isopropyl titanate to prepare thesolution. The mixture was refluxed for 21/2 hours in an oil bath atabout 70° to 80° C. and then distilled in vacuo.

Microanalysis of the fraction collected at 70°-80° C. and 0.5 millimeterof mercury showed 34.15 wt. percent carbon; 6.74 wt. percent hydrogen;and 27.53 wt. percent bromine.

The above fraction was mixed with an equal molar amount ofdi(isopropoxy) phosphoryl ethyl methyl diethoxysilane. An exothermicreaction occurred and a yellow oil solution was observed.

This polycondensation catalyst was used to produce a white polyester asabove described having a molecular weight of about 17,410 and a b-valueof 5.99.

EXAMPLE 3

The coordination complex component dichloro di(isopropyl) titanate wasproduced by preparing a solution of 521 grams (2.0 mole) of monochlorotri(isopropoxy) titanate prepared in Example 1 and 157 grams (2.0 mole)of acetyl chloride in a reaction flask (a standard 3 neck-round bottomflask) equipped with a mechanical stirrer, condenser and droppingfunnel. The acetyl chloride was slowly added to the monochlorotri(isopropery) titanate to prepare the solution. The mixture wasrefluxed for 2 hours in a oil bath at about 70° to 80° C. Microanalysisof the product fraction collected at 95°-98° C. and 1.0 millimeter ofmercury and showed 30.34 wt. percent carbon; 6.30 wt. percent hydrogen;and 28.48 wt. percent chlorine.

The above product, 0.8 moles (189.0 grams) of dichloro di(isopropoxy)titanate, was added to 261 grams (0.8 mole) of di(isopropoxy) phosphorylethyl methyl diethoxysilane. A exothermic reaction occurred and anorange oil soltion was observed.

The resulting catalyst was used to produce a polyester which had amolecular weight of about 17,000 and a b value of 4.3.

EXAMPLE 4

A polycondensation catalyst was prepared according to the invention bymixing equimolar amounts of monochloro tributoxy titanate anddi(methoxy)phosphoryl ethylmethyl diethoxysilane in an erlenmeyer flask.The product was a yellow oil.

The resulting catalyst was used to prepare a polyester which had amolecular weight of 24,500 and a b-value of 6.5.

EXAMPLE 5

The coordination complex component monobromo tri(butoxy) titanate wasproduced by preparing a mixture of 85 grams (0.25 mole) of tetrabutyltitanate and 30.74 grams (0.25 mole) of acetyl bromide in a reactionflask (a standard 3 neck-round bottom flask) equipped with a mechanicalstirrer, condenser and dropping funnel. The acetyl bromide was slowlyadded to the tetra butyl titanate to prepare the mixture. The mixturewas refluxed for 21/2 hours in an oil bath and at about 70° to 80° C.and subsequently distilled in vacuo. Microanalysis of the fractioncollected at 142°-152° C.; and 0.35 millimeters of mercury showed 41.38wt. percent carbon; 8.02 wt. percent hydrogen; 22.20 wt. percentbromine.

The product fraction, above, was mixed with an equal molar amont ofdi(methoxy) phosphoryl ethyl methyl diethoxysilane. A exothermicreaction occurred and a yellow oil solution was observed.

The resulting catalyst was used in the preparation of a polyester whichhad a molecular weight of 20,274 and a b value of 5.1.

EXAMPLE 6

The coordination complex component trichloro butoxy titanate wasproduced by preparing a mixture of 95.0 grams (0.5 mole) of titaniumtetrachloride and 37.0 grams (0.5 mole) of butanol in a reaction flask(a standard 250 milliliter 3 neck-round bottom flask) equipped with amechanical stirrer, condenser and dropping funnel. The titaniumtetrachloride was slowly added to the butanol. An ice bath was used tomaintain the reaction temperature under control owing to the exothermicnature of the reaction. A yellow solution was observed which uponstanding produced a white crystalline product. Microanalysis of theproduct after washing with hexane and drying in vacuo showed 21.77 wt.percent carbon; 4.62 wt. percent hydrogen; 45.30 wt. percent chlorine.

A portion of the above product (1.17 grams; 0.00515 mole) was mixed withan equal molar amount of di(isopropoxy) phosphoryl ethyl methyldiethoxysilane (1.678 grams; 0.00515 mole). A yellow oil was observed asthe product.

The resulting catalyst was used in the preparation of a polyester whichhad a molecular weight of 19,450 and a b-value of 3.4.

We claim:
 1. A polyesterification catalyst for the manufacture of solidfiber-forming polyesters or copolyester of dicarboxylic acid compoundsand aliphatic glycols comprising a coordination complex of (A) and (B),wherein:(A) is a metal alkoxy halide selected from the group consistingof

    M(OR).sub.a x.sub.b

wherein m is at least one of titanium, zinc, germanium, tin, lead,antimony and; R is alkyl, aryl, alkylaryl, arylalkyl, haloalkyl havingfrom 1 to 20 carbon atoms; a and b are integers having a value of from 1to 3; the sum of (a+b) is equal to or less than the integer 4; x is atleast one of F, Cl, Br or I; with the proviso that when M is antimony ais an integer having a value of from 1 to 4 and the sum (a+b) is equalto or less than 5; (B) is a silicon compound selected from the groupconsisting of: ##STR5## X is hydrogen or methyl and is methyl only whenm is one; R* is alkyl or haloalkyl having from 1 to 4 carbon atoms; R**is is methyl, ethyl, butyl, acetoxy, methoxy, ethoxy or butoxy; R ismethyl, ethyl, butyl, methoxy, ethoxy, butoxy, or trimethylsiloxy; R' ismethyl, methoxy, ethoxy, butoxy or trimethylsiloxy; R" is methoxy,ethoxy, butoxy, trimethylsiloxy or vinyldimethylsiloxy; R'" is methyl,ethyl, butyl or trimethylsilyl; Me is methyl; Z is methyl or T; Q is anNCCH₂ --, NH₂ CH₂ NHCH₂ --, NC--HS-- or HSCH₂ CH₂ S-- group; n is aninteger having a value of from 2 to 5; m is an integer having a value ofzero or one; x is an integer having a value of from 1 to 100; and y isan integer having a value of from 1 to 100;wherein the mole ratio of A:Bin said coordination complex is from 2:1 to 1:10.
 2. Apolyesterification catalyst as claimed in claim 1, wherein siliconcompound (B) is a compound of the general formula: ##STR6## wherein T,R, R, ', R" n and m are as defined in claim
 1. 3. A polyesterificationcatalyst as claimed in claim 1, wherein silicon compound (B) is acompound of the general formula: ##STR7## wherein Me, T and Z are asdefined in claim
 1. 4. A polyesterification catalyst as claimed in claim1, wherein silicon compound (B) is a compound of the general formula:##STR8## wherein Me, T, R'", x and y are as defined in claim
 1. 5. Apolyesterification catalyst as claimed in claim 1 wherein siliconcompound (B) is a compound of the general formula:

    QCH.sub.2 CH.sub.2 SiR.sub.3 **                            (IV)

wherein Q and R** are as defined in claim
 1. 6. A polyesterificationcatalyst as claimed in claim 1, wherein the silicon compound (B) isdiethoxyphosphorylethyl methyl diethoxysilane.
 7. A polyesterificationcatalyst as claimed in claim 1, wherein the silicon compound (B) is3-aminopropyl triethoxysilane.
 8. A polyesterification catalyst claimedin claim 1, wherein the silicon compound (B) is 2-cyanoethyltriethoxysilane.
 9. A polyesterification catalyst claimed in claim 1,wherein the silicon compound (B) is 2-mercaptoethyl triethoxysilane. 10.A polyesterification catalyst as claimed in claim 1, wherein saidpolyesterification catalyst is a coordination complex of monobromotri(iso-propoxy) titanate and di(isopropoxy) phosphoryl ethyl methyldiethoxysilane.
 11. A polyesterification catalyst as claimed in claim 1,wherein said polyesterification catalyst is a coordination complex ofmonochloro tri(isopropoxy) titanate and di(isopropoxy)phosphoryl ethylmethyl diethoxysilane.
 12. A polyesterification catalyst as claimed inclaim 1, wherein said polyesterification catalyst is a coordinationcomplex of dichloro(diisopropyl)-titanate and di(isopropoxy) phosphorylethyl methyl diethoxysilane.
 13. A polyesterification catalyst asclaimed in claim 1, wherein said polyesterification catalyst is acoordination complex of monochloro tri(butoxy)-titanate anddi(methoxy)phosphoryl ethyl methyl diethoxysilane.
 14. Apolyesterification catalyst as claimed in claim 1, wherein saidpolyesterification catalyst is a coordination complex of monobromotri(butoxy)titanate and di(methoxy)phosphoryl ethyl methyl diethoxysilane.
 15. A polyesterification catalyst as claimed in claim 1, whereinsaid polyesterification catalyst is a coordination complex of dichlorodiisopropoxy titanate and di(isopropoxy)phosphorylethyl methyldiethoxysilane.
 16. A polyesterification catalyst as claimed in claim 1wherein said polyesterification catalyst is a coordination complex oftrichloro butoxy titanate and di(isopropoxy) phosphoryl-ethyl methyldi(ethoxysilane).
 17. A polyesterification catalyst as claimed in claim1 wherein said polyesterification catalyst is a coordination complex ofdichloro di(isopropoxy) titanate and di(methoxy) phosphoryl ethyl methyldiethoxy silane.